invention s directed to a light waveguide lead comprising at least one light waveguide accommodated w thin a protective sheath that is embedded in a paste-like filling compound.
U.S. Pat. No. 4,370,023, whose disclosure is incorporated herein by reference thereto and which claims priority from the same German Application as European Patent 0 029 198 B1, discloses that light waveguides that are arranged within a protective sheath can be fi led with a spec f c filing compound or lead filling compound that is composed of a mixture of an oil, a thixotropic agent and an organic thickener. The demands which are made on such a lead filling compound are high because, first, the light waveguide should have adequate mobility within the filling compound so that the filling compound should, thus, be selected with an optimally low viscosity. However, the anti-drip reliability must also be assured for such a lead filling compound so that the lead filling compound dare not, even given vertical laying of the cable, move out or drip out of the interior of the protective sheath surrounding the light waveguide. The adequate resistance to dripping, on the one hand, and the gentle embedding of the light waveguide, on the other hand, in the filling compound must be guaranteed over a broad temperature range, for example from - 40.degree. C. through +80.degree. C.
In order to do justice to these demands, the filling compounds are manufactured of extremely high-grade substances, and this results in the fact that such filling compounds are relatively expensive.
In addition to lead filling compounds which are in immediate contact with the light waveguides, there also are what are referred to as core filling compounds that will fill the interspaces between electrical or optical leads and the outside cladding of the cable. For example, they are introduced into corresponding core spaces between these leads. Far lower demands are made of such core filling compounds than the demands which are made on the lead filling compounds, because, even in optical cables, the core filling compounds are not in immediate contact with the light waveguide but only in contact with potential protective sheaths of the light waveguides. In conjunction with such core filling compounds, German Patent 31 50 909 C2 discloses that hollow members can be introduced into the filling compound, whose walls, for example, can be composed of elastically viscous thermoplastics, thermoelastics or elastomers. The hollow members that are employed have an average diameter of approximately 40 .mu.m and a wall thickness of 0.6 .mu.m.